Trying to get a Zenith 16Z25 going for a fellow collector.
Tubes check good, detector diode test good. If's don't pass noise when probed, tuner osc is working per scope near proper freq 3 or 4. AGC makes no difference if adjusted. AGC at tuner is -1 volt and forcing + or - with a few external volts makes no difference.
The only schematic I could find is very blurry and I cant read values or volts.
Someone's been in there before me and that shakes my confidence in what I have before me.

Does anyone have tips to isolate? I feel I should be able to get snow but there is a IF, Tuner, AGC issue. What would be the if freq? I could try to inject a small signal and see if we are good there.

IDEAS?

Check the two 120K resistors connected to the low side of the secondary of the first video IF transformer. Have to disconnect, can't check in circuit.

Prev person replaced with 2 100k resistors w 120k. Do you think the value is critical? The IF amp tubes seem to be biased on G1 into conduction already. Got a bad feeling about the tuner. My goal at this time is to get a picture of any quality from a source to triage the set. The cabinet is good and CRT (original) is bright and sharp. It is however going to need caps, resistors and electrolytics. Being a widow maker chassis it is not likely to be a candidate for direct connection without a build up circuit to isolate.

I don't think those values would make much of a difference.

If you see noise crashes while changing channels its the tuner.
At that point check TNR B+, fila & RF AGC.
You can also make a junk box tuner subber with a click type SS tuner.
Just needs B+ & an AGC adjust & IF out.

73 Zeno

No noise while changing. also no noise when probing any of the IF's. Gut keeps telling me IF's. IF volts look good and G1 bias should be in into conduction. Played with AGC w/ external P.S. but no improvement. Still pondering, Detector diode checks good but maybe I'll sub it out.
A sharp schematic would be helpful, the owner may need to get one.